This proposal requests support for the development of an electron microscope facility to complement existing research facilities in making possible the principal investigator's research program. His research deals with ultrastructural and biochemical aspects of the contractile ring, which is the cellular organelle responsible for cytokinesis (cell cleavage). The specific aims of the research include detailed characterization of the contractile ring and its microfilaments, in situ and after isolation, in terms of their ultrastructure, biochemical composition, mode of action during cell division, and metabolic requirements for assembly, contraction and disassembly. Analyses of these kinds will enrich our understanding of cell division and should provide new opportunities for experimentally controlling cell proliferation through manipulation of the cell cleavage mechanism. The research methods to be employed include light and electron microscopy of living and preserved cells and of extracted cell "models". Experimental manipulations of living and extracted cells will be recorded by cinemicrography. Isolated contractile rings will be obtained by cell fractionation procedures and analyzed biochemically by standard procedures. Experimental material will include a diversity of marine invertebrate eggs, amphibian eggs and cultured mammalian cells.